There are known cogeneration systems in which a generator driven by an engine is used to produce electrical energy, and an exhaust heat exchanger is used to turn cold water into hot water using heat released by the engine, as disclosed in Japanese Patent Application Laid-Open Publication No. 08-004586 (JP 08-004586 A).
The disclosed cogeneration system is provided with a gas engine, a generator driven by the gas engine, and a hot water heat exchanger (“exhaust heat exchanger” hereunder) for turning cold water into hot water using heat released by the gas engine.
A basic method used for operating and controlling a cogeneration system involves setting an operation pattern of the cogeneration system according to the amount of hot feedwater needed on the output side.
According to this method, when there is little or no demand for hot feedwater, a gas engine 1 is stopped so that the temperature thereof does not reach or exceed a predetermined value. Specifically, according to this method, supplying hot water is prioritized over supplying electricity. However, during power outage, for example, it has been necessary to attach a separate cooling unit to the gas engine and cool the gas engine, e.g., in order to provide a continuous supply of electrical energy.